OCTAHEDRAL AND PRISMATIC ISOMERS OF CRF6 - ENERGIES AND VIBRATIONAL FREQUENCIES

Detailed ab initio electronic structure calculations are reported for octahedral and prismatic isomers of CrF6. A carefully graded series of basis sets has been used. Correlation effects were calculated at the CCSD(T) level, and some exploratory MR-CISD calculations were performe d. Vibrational frequencies calculated at the SCF level are reported. I n agreement with other recent work, the octahedral isomer is shown to be the most stable for CrF6; the crucial role played by f functions in the Cr basis is emphasized. Triple excitations preferentially stabili ze the octahedral isomer. Our final value for the octahedral-prismatic energy electronic energy separation is 59.3 kJ/mol, which is much low er than the CASPT2 result reported by Pierloot and Roos (Inorg. Chem. 1992, 31, 5353).